The purpose of this study is to evaluate the safety and efficacy of nemtabrutinib (formerly ARQ 531) in participants with hematologic malignancies of chronic lymphocytic leukemia (CLL)/ small lymphocytic lymphoma (SLL), Richter's transformation, marginal zone lymphoma (MZL), mantle cell lymphoma (MCL), follicular lymphoma (FL), and Waldenström's macroglobulinemia (WM).